1. Field of the Invention
This invention pertains to sprayers, particularly high-pressure, vehicle powered insecticide sprayers in which a fluid additive, such as an insecticide, is accurately added to a high-pressure water flow at the nozzle of the sprayer.
2. Description of the Prior Art
For many years, sprayers for controlling weeds or insects, both in agricultural areas and in urban areas, have used bulk spray units in which a large tank of premixed spray is dispensed by truck or airplane over the infected area. That procedure presents problems in shelf life of the mixed spray as well as adverse environmental damage when the spray is disposed of.
An improved technique for spraying has been developed in which the additive fluid, such as an insecticide, is metered into the water just upstream of the spray nozzle. In this technique, the spray solution is not premixed in bulk, resulting in minimal wastage and eliminating need for dumping or disposing of the toxic additive fluid. It is difficult, however, in high-pressure spraying equipment, such as at a water pressure of 800 psi, to obtain accurate proportioning of the additive fluid into the water during all phases of operation of the sprayer. One suitable apparatus is illustrated in U.S. Pat. No. 3,865,308. The apparatus of that patent application, however, is extremely expensive to manufacture and maintain and thus has limited market potential.